Method for manufacturing thin sheet filter media



l... V. GEWISS METHOD FOR MANUFACTURING THIN SHEET FILTER MEDIA FiledJune 7. lees e 0 F c 0 k\ i 2 ,l

most completely from the former and'findsitselhafterv 3,245,322 drying,concentratedat the latter two. In this way, the

THOD )FOR MANUFACTURING THKN SHEET FILTER MEDIA Lucien Victor Gewiss,Ville dAvray, France, assigner to Marc Wood Societe Anonyme pour laPromotion des States Patent O Exchange rTechniques internationaux,Paris, France, a

company of France Filed .lune 7, 1962, Ser. No. 200,776 Claims priority,application France, .lune 12, 196i, 864,644, Patent 1,305,974 7 Claims.(Cl. 117-4) The dominant preoccupation of manufacturers of sheetso-called full ow filtration, only by producing `filter papers of athickness substantially greater than 0.3 mm. in fact, it is only bymaking the sheet of fibers of a certain thickness that, vfor an equalmechanical resistance, it seems possible,considering the means ofmanufacture presently used, to maken filter sheet of great =permeabilitywhich clogs only after having provided sepvice of ,substan tialduration. Experience shows that. for.` anv equal mechanical resistance,thin filter'sheetsalwayshave a lower and less uniform permeabilitythanthick sheets.

Now it can be imagined that if itwere possible to have, particularly forfull liow filtration, filter` sheets which, while offering goodpermeability, would be substantially thinner than those presentlyavailable, it would be possible, even if these sheets had substantiallyless mechanical resistance, by applying certain known folding methodswhich make it possible to form iilter elements of small dimensions, tosave even more substantially on the volume of the latter and,consequently, to offer the industry iil tration units of smallerdimensions and lower price than those which presently exist.

"the present invention has as its object a simple process,

both easy and economical to apply, which makes it possible to obtainfilter sheets which comply with these conditions. it also comprisesapparatus for applying this process and, by way of new industrialproducts, filter sheets obtained by said process.

The process according to the invention essentially comprises subjectinga iilter sheet of the usual constitution and thickness to animpregnation treatment by a substance designed to bind the fibers of thesaid sheet togather at the points whfe they Contact each other,concentrating such impregnated substance on the two external faces ofthe sheet, and dividing this sheet into two parts by a splittingoperation effective along its mean crosssection.

ln this way two lter sheets are obtained each having a thicknesssubstantially equalto half the thickness of the initial sheet and havingcertain remarkable properties which will be hereinafter set forth.

In the practical application of the invention, the impregnation of theinitial filter sheet can be effected, in a manner already known, bydipping it in the desired solu tion of an appropriate synthetic resin,kfor example a resin solution of the urea-formaldehyde in ethyl alcoholtype, after which the evaporation ofthe'solvent is insured in such amanner that the evaporation takes place in an equal manner on both facesof the sheet.

During the course of the evaporation, the impregnation substance, whichmigrates in the direction of the evaporation of the solvent, i.e. fromthe median cross-section of the sheet toward the two outside faces,disappears a1- two outside faces of the sheet nd themselves constituted,independently of each other, of fibers solidly anchored 4, to each otherby the resin while their mutual central zone consists only of anassembly of `unbound fibers held to gether only by their normal initialintertwinng., It is therefore easy to separate progressively thetwfobutside y half sheets from each other since by pulling them apartnothing prevents the intermediate bers from disengaging from each other.f

The operation of splitting the sheet can be done by hand v though it isdesirable to proceed with caution lso 'as vto progress very evenly alongas straight aline of separation as possible. place without diiicultyprovided the angle of separation selected is the most favorable and doesnot vary between too broad limits. v

It should be noted that the two facesfof each ofthe two split thinsheets obtained by the above-describcd process are not, of course,identical. @ne is in fact strongly impregnated while the other is muchlessso. Also, the

first facefis relatiyel'ysmooth while the second isshaggy.

When such-.aslicetfis used 'for making folded :litter clements, ,.i'ts,shaggy side can advantageously be laken, ad.

" f @manna vantage ofeither to increase the amount retained beforeclogging due tothen' e' surface which results, or else to increase tharein contact with eachother.;

For 'the case where.. it would appear ing process. The followingdescription with can be practiced. ln the drawings:

FIG. l is a schematic elevation view of one method of executing aninstallation which makes it possible Ato perform the impregnation, thedryingy and thesplittihg-of the initial sheet in a continuous process;

FIG. 2 is a schematic cross-section of a device whichl can be used toreduce or to even out the height of the shaggy fibers ou the split faceof each of the thin sheets ln the example represented in 1, theinstallation f shown).` Downstream from these two cylinders, the con-'tinuous sheet 1 plunges into a closed tub Swithin" which is locatedthemixture required for ,the impregnation, for"` Y example a solution ofureafformaldehyde rcsininethyl alcohol which is constantly maintainedatl the desirable concentration. The continuous sheet -1 comesout-of'tub5 under the action of two wringing cylinders 6 and 7' I which have thefunction of extracting from thelter sheet the excess of liquid itcontains. Upon coming out of tub 5, continuous sheet i zigzag passage ofgreat lengthconssting of vertical compartments 9a, 9b 9f, and of ahorizontal compart- 3,245,822' Patented Apr. l2,

Mechanically, the splitting operation takes isses si l filter huidbetween surfaces .downstream from sheets which` aient i6 reduce, thethickness of the shaggy face, it is easy toremove the excess length offibers by means of an appropriate'grindl.

reference to theV an# nexed drawings, given by way of non-restrictiveexam ples, will malte it readily understood how the invention risesvertically4 up to roller 8 which enables it to change direcy tion and toenter a drying oven 9 made in the form of athen horizontally incompartment 9g. Continuousv sheet 1 comes vertically out-of the dryingoven downstreamifrom roller i101: where it passes between two cylinders11 and 12 which serve both to guide and to split the sheet. It is vwhenit cornes out from between these two cylinders-that the splittingvofcontinuou's sheet 1 takes place intotwo thin sheets 1a and 1b; Thissplitting istinitiaDystarte'd by hand, after which it-proceedsmechanically, the two sheets 1a and 1b being reeled onto two rolls 13and 14 driven in rotation by appropriate motors (not represented). Nat`urally, the usual appropriate means (likewise not represented) areprovided for automatically regulating the will be subjected to aconstant traction force.

The ventilation necessary for drying the continuous sheet of paper 1which-moves continuously in drying adjacent said faces.

oven 9 in the direction of arrows f is insured by an assernbly designednot only to move lthe masses of air used for this purpose in thedirection of arrows F, but

also to maintain these masses at the highest acceptabletemperature whichdoes not'result in a premature polymerization of the impregnationsubstance used (this polymerization bein-g best deferred until after thefilter elements are manufactured);I This assembly, which is moreoverdesigned Ito insure the recovery of the solvent vapors (which, by reasonof their toxicity and their commercial value cannot be discharged intothe atmosphere) has not been represented indetail since it relates to aknown techniqueg'only blower 15 which is a part of such an assembly hasbeen represented, for the purposes of the schematic drawing, at one endof horizontal compartment 9g. l

As indicated above, 'the length `of the shaggy bers on the split face ofeach of the thin sheets obtained can be reduced or e-vened out by agrinding process. FIG. 2 represents schematically a device designed tobe used for this purpose. It comprises a table 16 above which the sheetof thin paper, ia for example, is caused to move continuously, shaggyside up. A roller 17 is provided at one end of table lo in order tocause sheet la to change direction sharply and to hold it taut on thetable. Parallel to the latter and above it is located a grinding wheeli3 whose abrasive surface 19 protrudes slightly beyond its lower steelface 20. The latter is in contact with the still shaggy face of sheet 1ain order to keep the sheet pressed against table 1 6 over its entirelength. The adjustment of the space between the -table and abrasive vsurface i9 of the grinding wheel can be effected by conventional means,the motor which drives the grinding wheel being mounted on a carriagesusceptible of being moved vertically on slides by means off amicrometric screw, for example.

' The invention may be embodied in other speciiic forms withoutdeparting from the spirit or essential characteristics thereof.Thepresent embodiment is therefore to be considered in all respects asillustrative and not restrictivethe scope of the invention bein-gindicated by `theappended claims rather than by the foregoing descrip- 4tion, and all changes 'which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:

l. A process for. making a plurality of sheets of fibrous material froma single ply sheet of said material comprising thoroughly impregnating-said sheet with a solution of resinous binder material contained in anevaporatable carrier; evaporating said carrier from both faces ol saidsheet so as to cause said binder material to migrate to and concentrateat points adjacent said faces of said sheet; and separating said sheetinto a plurality of sheets along a plane substantially parallel Ito andbetween said faces and which passes .through a portion of said sheethaving a lesser concentration of binder material than y2. A process asdened in claim 1 wherein said binde! matlelrial is chemically unreactivewith said iibrous materi 3. A process as defined in claim 1 wherein saidbinder material is a urea-formaldehyde resinl and said carrier is ethylalcohol. 4. A process as defined in claim 1 wherein said binder is apolymerizable material, said binder being in an incomplete state ofpolymerization at the time said separation step is carried out.

5. A process as dened in claim 1 wherein said plane is mediallypositioned between said two faces of said sheet and is substantiallyparallel thereto'.

6. A process as delned in claim .1 wherein said evaporation takes placethrough the application of substantially equal quantities of heat toeach face of said sheet.

7. A process -for making a plurality of sheets of iibrous material froma single ply sheet of said material .comprising thoroughly impregnatingsaid sheet with a solu- -tion of synthetic resin binder materialcontained in an evaporatable carrier; e-vaporating said carrier fromboth faces of said sheet lso as to cause said binder material to migrateto and concentrate at pointsadjaoent said faces of said sheet; andseparating said sheet into a plurality of sheets along a planesubstantially parallel to and be tween said faces and which passesthrough a portion ol said sheet having a lesser concentration of binderma. terial than adjacent said faces.

References Cited by the Examiner UNITED STATES PATENTS 1,459,499 6/ 1923Brown et al.` l56-254 1,465,541 8/1923 Brown et'al. 156-254 2,058,50210/1936 Quinn 51-72 2,092,967 9/1937 Gay et al. 117-4 2,195,239 3/ 1940Champsaur 156-254 2,368,024 1/1945 Himmell 117--4 2,587,171 2/ 1952Knewstuff et al. 154-254 2,644,780 7/ 1953 Simkins et al. 156-2542,676,128 4/1954 Piccard 156-46 2,709,146 5/1955 Berry 156-254 2,762,1709/ 1956 Hunziker 51-72 2,765,247 10/1956 Graham 154-46 EARL, M. BERGERT,Primary Exminer. DOUGLAS I. DRUMMOND, Examiner.

1. A PROCESS FOR MAKING A PLURALITY OF SHEETS OF FIBROUS MATERIAL FROM ASINGLE PLY SHEET OF SAID MATERIAL COMPRISING THOROUGHLY IMPREGNATINGSAID SHEET WITH A SOLUTION OF RESINOUS BINDER MATERIAL CONTAINED IN ANEVAPORATABLE CARRIER; EVAPORATING SAID CARRIER FROM BOTH FACES OF SAIDSHEET SO AS TO CAUSE SAID BINDER MATERIAL TO MIGRATE TO AND CONCENTRATEAT POINTS ADJACENT SAID FACES OF SAID SHEET; AND SEPARATING SAID SHEETINTO A PLURALITY OF SHEETS ALONG A PLANE SUBSTANTIALLY PARALLEL TO ANDBETWEEN SAID FACES AND WHICH PASSES THROUGH A PORTION OF SAID SHEETHAVING A LESSER CONCENTRATION OF BINDER MATERIAL THAN ADJACENT SAIDFACES.